Quantitative Neuromuscular Monitoring

Educational Objectives

The goal of this program is to improve the management of neuromuscular monitoring (NMT). After hearing and assimilating this program, the clinician will be better able to:

1. Appreciate the limitations of qualitative NMT.
2. Evaluate various sites for NMT.
3. Compare currently available modalities for quantitative NMT.

Summary

Residual neuromuscular blockade (NB; RNB): multiple studies show that 20% to 40% of adult patients have RNB after extubation; these patients are at risk for airway obstruction, hypoxemic episodes, aspiration, and postoperative respiratory complications, and may have unpleasant symptoms of muscle weakness; they also have longer stays in the post-anesthesia care unit (PACU), are more likely to be admitted to the intensive care unit, and give clinicians lower patient satisfaction scores on postoperative surveys

Occurrence of RNB: clinical signs (eg, 5-sec head lift, grip strength) are subjective and are not reliable indicators of full NB recovery; respiratory parameters (eg, tidal volume, vital capacity, minute ventilation, negative inspiratory force) are also unreliable; the diaphragm recovers before any of the sites used to monitor NB; these signs are usually unreliable in predicting the dose of reversal agents or complete recovery

Reversal agents: sugammadex (SUG) only reverses the action of aminosteroid agents and does not reverse benzylisoquinolines; studies have shown ≈10% RNB when using SUG; SUG decreases the RNB but does not completely eliminate it; neostigmine has its own limitations, ie, it cannot reverse profound or deep blocks, and it can cause paradoxical muscle weakness; the rates of NB in pediatric patients are similar to adults; data — Ledowski et al (2015) reported an overall rate of 28% and 6.5% with severe blocks; Klucka et al (2019) reported a rate of 48% before extubation and ≈27% in the PACU; Vested et al (2020) analyzed patients <3 yr of age who received a single dose of cisatracurium and found 16% had RNB, and the single dose of cisatracurium lasts ≤240 min; Faulk et al (2024) reported 30% RNB with neostigmine

RNB in infants and neonates: infants and neonates are at risk for several reasons, including immature respiratory control and protective airway refluxes, smaller and more collapsible airways, and smaller functional residual capacity; all these parameters are affected by NB; this jeopardizes airway patency and threatens oxygenation; these patients are more sensitive to rocuronium because of organ immaturity and decreased acetylcholine in the motor nerves; Gilbertsonet al (2021) studied patients who received rocuronium for pyloromyotomy and reported an odds ratio for neostigmine nonreversibility at the end of surgery of 1.36 for every 0.1 mg/kg above 0.5 mg/kg administered; Faulk et al analyzed electromyography (EMG) vs acceleromyography and found that, with 0.5 mg/kg of rocuronium, patients went to complete block quickly, regained the first twitch in ≈1 hr, and usually required ≈2 hr for complete recovery; patients who received >1 mg/kg did not completely recover even after 2 hr; RNB in children may also be misdiagnosed, most commonly mistaken for emergence agitation; treatment with sedatives worsens respiratory mechanics, potentiating postoperative respiratory complications

Neuromuscular monitoring in practice: Faulk et al (2021) — a survey asked clinicians about neuromuscular monitoring in their clinical practice; ≈60% use only qualitative monitors, 15% use only quantitative monitoring, and 23% use both; clinicians who were trained before the introduction of SUG were more likely to always use monitors (40%); 30% of clinicians trained after the introduction of SUG use monitors only on a case-by-case basis

American Society of Anesthesia (ASA) practice guidelines: these guidelines address monitoring and antagonism of NB; the goal is to enhance patient safety by reducing RNB; they recommend against using only clinical assessments and recommend using quantitative monitoring to ensure train-of-four (TOF) ratio ≥0.9; these were strong recommendations with moderate strength of evidence to support them; TOF count is the number of twitches out of 4, while the TOF ratio is the ratio of the height of the fourth twitch to the first twitch; the TOF ratio is lower with deeper levels of block; ASA guidelines recommend the adductor pollicis as the preferred site for monitoring; ASA also recommend SUG over neostigmine except in patients administered with atracurium or cisatracurium; neostigmine can be used as an alternative if there is a minimal depth of blockade with TOF ratio of 0.4 to 0.9; no reversal agent is required for a TOF ratio >0.9

Adductor pollicis: upper airway muscles are critical to maintaining airway patency and protection from aspiration; these muscles are very sensitive to neuromuscular blocking drugs and do not recover until TOF is near baseline; if the adductor pollicis has recovered, the upper airway muscles should also be recovered; clinicians commonly use facial muscles for monitoring because of their easy access in most cases, however, they are more resistant to block and recover before the recovery of adductor pollicis and upper airway muscles; they are also more prone to direct stimulation, resulting in an overestimation of the degree of recovery; the diaphragm recovers before any of these peripheral muscles, so relying on respiratory parameters also overestimates the degree of recovery

Qualitative and quantitative monitors: ASA prefers quantitative monitoring as it reduces the risk for RNB

Development of peripheral nerve stimulators: this qualitative monitor was originally introduced in the 1950s as a single stimulus; by the 1970s, TOF counts were developed; these devices deliver current impulses to the peripheral nerve, and subjective assessment is used to determine reversal of NB; TOF counts count the number of twitches when stimulation is delivered; post-tetanic count refers to the number of counts after sustained tetany; fade refers to the decrement in the signals from the first to fourth twitch; fade is clinically imperceptible if the TOF ratio is between 0.4 and 0.9

Quantitative monitors: the only monitors available for detecting a TOF ratio between 0.4 and 0.9; measure RNB and display numerical results; can assess whether the TOF ratio is >0.9, indicating full recovery with no clinically significant weakness; multiple types of quantitative monitors are available

Mechanomyography: has been the historical standard but has been used only in research and not in clinical practice; requires a complex setup, and a 200- to 300-g muscle preload must be maintained; precise and reproducible

Kinemyography: measures the bending of a piezoelectric sensor placed in the thenar web space when the muscle contracts; requires a free thumb with no barrier to thumb movement; overestimates the degree of recovery

Acceleromyography: one of the most commonly used monitors in clinical practice; a piezoelectric sensor measures the acceleration of muscle contraction; the sensor is attached to the muscle, eg, on the thumb; the electrode on the wrist stimulates the ulnar muscle, and movement is sensed by the transducer; voltage is generated by a crystal in the sensor and analyzed by the monitor; the monitor calculates the TOF ratio; requires a free limb and requires 5 to 10 min to set up; calibration and assessment of a baseline is required before delivering any neuromuscular blocking drug; the baseline ratio is calculated to be >1 (≤1.2 in some patients); the 0.9 of baseline is calculated by multiplying the 0.9 by the baseline ratio (eg, if the baseline is 1.2, 1.08 [product of 1.2 and 0.9] is the number needed to indicate full recovery [residual weakness at 0.9 in this case]); cannot be used in awake patients; has limited utility in the PACU; there is a considerable learning curve for using the monitor

Electromyography: the simulating electrode is attached to the wrist for the ulnar nerve; the electrode measuring the compound action potential of the muscles is at the adductor pollicis; the monitor measures the electrical signal from the muscle; this signal is not susceptible to changes in contractility (ie, a free limb is not a prerequisite, offering benefit to pediatric populations) but is subject to motion artifact, electrocardiography artifact, and to noise and electrical equipment; maximum stimulus amplitude should be noted; excessively high stimulus amplitude may result in inaccurate baseline; can be used on PACU patients without excessive pain; some currently available monitors can be calibrated within 7 to 15 sec; the monitor shows the twitch height, EMG signal, and graphical representation; the clinician can also deliver tetanic stimulus and measure post-tetanic counts; post-tetanic counts increase as the patient recovers toward one twitch, which can help with dosing reversal agents; pediatric population — EMG quantitative monitors are easy to use, accurate, and reliable; specific pediatric-size sensors are available; the arms can be tucked; a baseline is recommended but not required as it is for acceleromyography

Cost-effectiveness: quality improvement project at the speaker’s institution — demonstrated cost savings using quantitative monitors; the first component involved creation of aliquots of SUG; the pharmacy was able to obtain 500-mg vials and aliquot them into 50-mg syringes; pediatric patients rarely require 50 to 100 mg of SUG; the aliquots were prepared by pharmacy technicians during downtime, so this component was considered to have no cost; the second component was the introduction of quantitative monitors; after adjusting for the upfront cost and the sensor cost, the estimated savings were calculated to be $373,000/yr based on reduced use of SUG in ≈8000 pediatric anesthetics using rocuronium annually

Barriers to implementation: significant training is required for anesthesia professionals and nursing staff to use these monitors; having a team dedicated to helping staff learn to apply and use the monitors is beneficial; easy accessibility is key to integrating the monitors into practice; the TOF ratio and TOF count can be integrated into the electronic medical record

Readings

Azizoğlu M, Özdemir L. Quantitative neuromuscular monitoring with train-of-four ratio during elective surgery: A prospective, observational study. J Patient Saf. 2021;17(5):352-357. doi:10.1097/PTS.0000000000000874; Eikermann M, Groeben H, Hüsing J, et al. Accelerometry of adductor pollicis muscle predicts recovery of respiratory function from neuromuscular blockade. Anesthesiology. 2003;98(6):1333-1337. doi:10.1097/00000542-200306000-00006; Faulk DJ, Austin TM, Thomas JJ, et al. A Survey of the Society for Pediatric Anesthesia on the Use, Monitoring, and Antagonism of Neuromuscular Blockade. Anesth Analg. 2021;132(6):1518-1526. doi:10.1213/ANE.0000000000005386; Faulk DJ, Karlik J B, Strupp K M, et al. The incidence of residual neuromuscular block in pediatrics: A prospective, pragmatic, multi-institutional cohort study. 2024. Cureus. 16(3): e56408. doi:10.7759/cureus.56408; Gilbertson LE, Fiedorek MC, Fiedorek CS, et al. Prolonged neuromuscular block after rocuronium administration in laparoscopic pyloromyotomy patients: A retrospective bayesian regression analysis. Paediatr Anaesth. 2021;31(3):290-297. doi:10.1111/pan.14118; Klucka J, Kosinova M, Krikava I, et al. Residual neuromuscular block in paediatric anaesthesia. Br J Anaesth. 2019;122(1):e1-e2. doi:10.1016/j.bja.2018.10.001; Lee W. The latest trend in neuromuscular monitoring: return of the electromyography. Anesth Pain Med (Seoul). 2021;16(2):133-137. doi:10.17085/apm.21014; Ledowski T, O'Dea B, Meyerkort L, et al. Postoperative Residual Neuromuscular Paralysis at an Australian Tertiary Children's Hospital. Anesthesiol Res Pract. 2015;2015:410248. doi:10.1155/2015/410248; Luo J, Chen S, Min S, et al. Reevaluation and update on efficacy and safety of neostigmine for reversal of neuromuscular blockade. Ther Clin Risk Manag. 2018;14:2397-2406. Published 2018 Dec 10. doi:10.2147/TCRM.S179420; Thilen SR, Weigel WA, Todd MM, et al. 2023 American Society of Anesthesiologists Practice Guidelines for Monitoring and Antagonism of Neuromuscular Blockade: A Report by the American Society of Anesthesiologists Task Force on Neuromuscular Blockade. Anesthesiology. 2023;138(1):13-41. doi:10.1097/ALN.0000000000004379; Vested M, Tarpgaard M, Eriksen K, et al. Incidence of residual neuromuscular blockade in children below 3 years after a single bolus of cisatracurium 0.1 mg/kg: A quality assurance study. Acta Anaesthesiol Scand. 2020;64(2):168-172. doi:10.1111/aas.13495.

Disclosures

For this program, members of the faculty and planning committee reported nothing relevant to disclose.

Acknowledgements

Dr. Strupp was recorded at the 62nd Clinical Conference in Pediatric Anesthesiology, held February 16-18, 2024, in Anaheim, CA, and presented by the Pediatric Anesthesiology Foundation, Children’s Hospital Los Angeles. For information on future CME activities from this presenter, please visit https://peds-gas.org/. Audio Digest thanks the speakers and presenters for their cooperation in the production of this program.

CME/CE INFO

Accreditation:

The Audio- Digest Foundation is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.

The Audio- Digest Foundation designates this enduring material for a maximum of 1.00 AMA PRA Category 1 Credits™. Physicians should claim only the credit commensurate with the extent of their participation in the activity.

Audio Digest Foundation is accredited as a provider of continuing nursing education by the American Nurses Credentialing Center's (ANCC's) Commission on Accreditation. Audio Digest Foundation designates this activity for 1.00 CE contact hours.

Lecture ID:

AN662201

Expiration:

This CME course qualifies for AMA PRA Category 1 Credits™ for 3 years from the date of publication.

Instructions:

To earn CME/CE credit for this course, you must complete all the following components in the order recommended: (1) Review introductory course content, including Educational Objectives and Faculty/Planner Disclosures; (2) Listen to the audio program and review accompanying learning materials; (3) Complete posttest (only after completing Step 2) and earn a passing score of at least 80%. Taking the course Pretest and completing the Evaluation Survey are strongly recommended (but not mandatory) components of completing this CME/CE course.

Estimated time to complete this CME/CE course:

Approximately 2x the length of the recorded lecture to account for time spent studying accompanying learning materials and completing tests.